Data from: Proteomic evidence of a paedomorphic evolutionary process within a marine snail species: a strategy for adapting to extreme ecological conditions?

The exposed and sheltered ecotypes of the marine snail Littorina saxatilis from European rocky shores are considered a key model system to study adaptation and ecological speciation. Previous studies showed that two ecotypes (RB and SU) of this species in NW Spain have differently adapted to different shore levels and microhabitats. In order to understand how this divergent adaptive process has been accomplished, we followed a quantitative proteomic approach to investigate the proteome variation in a number of different biological factors, i.e. ecotype, ontogeny and their interactions. This approach allowed testing the hypothesis that one of the ecotypes has evolved by paedomorphosis, and also whether or not the molecular mechanisms related to ecotype differentiation are set up in early developmental stages. Additionally the identification of some candidate proteins by mass spectrometry provides some functional insights about these evolutionary processes. Results from this study provided evidence of higher ontogenetic differentiation at proteome level in the RB (metamorphic) than in SU (paedomorphic) ecotype that point to the possibility of juvenile stage retention in this latter ecotype. The level of protein expression (proteome) differences between ecotypes maintained nearly constant from late embryonic stages to adulthood, although some proteins involved in these changes considerably differed in embryonic compared to other ontogenetic stages. Paedomorphosis may be the evolutionary response of the SU ecotype of solving the trade-off during sexually immaturity that is caused by the evolution of small size arising from adaptation to the wave exposed habitat. Some potential candidate genes of adaptation related to energetic metabolism have been identified, providing a promising baseline for future functional analyses.

采自欧洲岩岸的海洋滨螺（Littorina saxatilis）的暴露型与遮蔽型生态型，是研究适应性演化与生态物种形成的关键模式系统。既往研究显示，分布于西班牙西北部的该物种两个生态型——RB与SU，已分别适应了不同的潮间带高程与微生境。为阐明该趋异适应性演化过程的实现机制，本研究采用定量蛋白质组学方法，探究了生态型、个体发育及其交互作用等多个生物学因子下的蛋白质组变异。该研究策略可用于检验两项假说：其一，其中一个生态型通过幼态持续（paedomorphosis）演化而来；其二，与生态型分化相关的分子机制是否在发育早期即已建立。此外，通过质谱法（mass spectrometry）鉴定得到的若干候选蛋白，也为解析此类演化过程提供了功能层面的新见解。本研究结果表明，RB生态型（变态型）的蛋白质组水平个体发育分化程度高于SU生态型（幼态持续型），这提示后者可能存在幼体阶段滞留现象。尽管部分参与该过程的蛋白质在胚胎期与其他发育阶段的表达存在显著差异，但生态型间的蛋白质表达（蛋白质组）差异水平从胚胎晚期至成体期基本保持稳定。SU生态型的幼态持续演化，可能是其为解决因适应浪击生境演化出小型体型所导致的性成熟前适应性权衡问题的演化策略。本研究还鉴定出若干与能量代谢相关的适应性潜在候选基因，为后续功能分析提供了颇具前景的研究基础。